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The Terminator
Engine/Tuning
Help- Fuel issue
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<blockquote data-quote="tv’s 03" data-source="post: 16643374" data-attributes="member: 201844"><p>Hi All, I was here a long time ago, but it didn’t recognize my user name anymore. Glad to be back. </p><p></p><p>I did a build on my 03 over the winter and can’t figure out my issue. Car has a Whipple gen 4 2.9. 3.5 upper, stock lower. I took it to the dyno to have a big name tuner tune it. After the initial data log with a start up tune. All looked good. But when we got to the dyno it was cutting out as soon as you went with.</p><p></p><p>tuner says it’s an issue with the fuel pumps, which are new Walbro improved GT supercar pumps. Modified FPDM, pprv delete, and dash 8 line from tank to stock fuel rail and huge AFCO race filter feeding FIC 1000’s. </p><p></p><p>tuner says that they don’t like the pulse width modulations for the returnless system. He wants me to spend another $700 to covert it to a “poor man’s return system”. I don’t think I need to do that, as this system is pretty robust. It may need the wire upgrades, but should make it past the initial stab and a dyno tune.</p><p></p><p>so that’s the backstory. I trying to figure out what’s wrong. Fuel pressure at the rail is dropping under wot. Fuel pressure drop across the injectors show the same exact numbers as fuel rail pressure. It hold 39-40 psi just driving around and drives great. I swapped out my frps for good measure, no change, checked for vacuum at the sensor, good. When I unplug the vacuum line and block it off, car runs exactly the same. It’s seems like the pcm is not recognizing vacuum at all. </p><p></p><p>could one of my pumps be bad, or is this a pcm issue? Any ideas? I need help</p></blockquote><p></p>
[QUOTE="tv’s 03, post: 16643374, member: 201844"] Hi All, I was here a long time ago, but it didn’t recognize my user name anymore. Glad to be back. I did a build on my 03 over the winter and can’t figure out my issue. Car has a Whipple gen 4 2.9. 3.5 upper, stock lower. I took it to the dyno to have a big name tuner tune it. After the initial data log with a start up tune. All looked good. But when we got to the dyno it was cutting out as soon as you went with. tuner says it’s an issue with the fuel pumps, which are new Walbro improved GT supercar pumps. Modified FPDM, pprv delete, and dash 8 line from tank to stock fuel rail and huge AFCO race filter feeding FIC 1000’s. tuner says that they don’t like the pulse width modulations for the returnless system. He wants me to spend another $700 to covert it to a “poor man’s return system”. I don’t think I need to do that, as this system is pretty robust. It may need the wire upgrades, but should make it past the initial stab and a dyno tune. so that’s the backstory. I trying to figure out what’s wrong. Fuel pressure at the rail is dropping under wot. Fuel pressure drop across the injectors show the same exact numbers as fuel rail pressure. It hold 39-40 psi just driving around and drives great. I swapped out my frps for good measure, no change, checked for vacuum at the sensor, good. When I unplug the vacuum line and block it off, car runs exactly the same. It’s seems like the pcm is not recognizing vacuum at all. could one of my pumps be bad, or is this a pcm issue? Any ideas? I need help [/QUOTE]
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